/etc/unbound/unbound.conf.d/forward.conf
# unbound  forward-zone output
for IP in $(consul catalog nodes | grep ctl | cut -d " " -f6); do
    echo "  forward-addr: ${IP}@53"
done
systemctl restart unbound

# disable IPv6
# /etc/unbound/unbound.conf.d/server.conf 
server:
...
   do-ip6: no

# flush zone
unbound-control flush_zone dev.example.com

Links
https://wiki.alpinelinux.org/wiki/Setting_up_unbound_DNS_server
https://calomel.org/unbound_dns.html